A passive optical network (Passive Optical Network, PON) technology is a point-to-multiple-point (P2MP) optical access technology. A PON network is formed by an optical line termination (Optical Line Termination, OLT), an optical splitter, an optical network unit (Optical Network Unit, ONU) or an optical network terminal (Optical Network Terminal, ONT), and a fiber that connects such devices.
As a device at a central office end, the OLT is connected with an optical splitter (Optical splitter) or an extender box (EB, Extender Box) through a backbone fiber, and the optical splitter or the EB is connected with each ONU through a separate branch fiber. There is a backbone fiber between the optical splitter or the EB and the OLT, and there are a number of branch fibers between the optical splitter or the EB and the ONU. In the downlink direction (from the OLT to the ONU), the optical splitter or the EB implements an optical splitting function, and sends downlink optical signals of the OLT to all ONUs through the branch fibers; and, in the uplink direction (from the ONU to the OLT), the optical splitter or the EB implements an optical signal aggregation function, and aggregates optical signals sent by all ONUs, and sends the signal to the OLT through the backbone fiber.
Currently, to resist a fault of the backbone fiber between the optical splitter or the EB and the OLT or an OLT fault, a 1+1 protection architecture shown in FIG. 1 is generally adopted, in which an active backbone fiber, a standby backbone fiber, an active OLT and a standby OLT are used to provide 1+1 protection for the backbone fiber and the OLT. When the backbone fiber or the OLT is faulty, the standby OLT takes over the ONU under the original active OLT. An aggregation node (Aggregation Node, AggN, or Aggregation Switch, AGS) is connected with the active OLT and the standby OLT through an active port and a standby port (such as an Ethernet physical port or an Ethernet logical port) respectively; or, there are also an active aggregation node and a standby aggregation node, and the active aggregation node and the standby aggregation node are connected with the active OLT and the standby OLT respectively.
The inventor of the present invention finds that when the active OLT is faulty or the backbone fiber between the active OLT and the optical splitter or the extender box is faulty, data packet forwarding performed in the active OLT needs to be switched to the standby OLT. The existing method of switching from the active OLT to the standby OLT is based on selecting, by a physical port of the active OLT which is used to forward a data packet, a physical port of the standby OLT to take over the forwarding of the data packet, where the standby OLT corresponds to the physical port of the active OLT. However, when a data packet is forwarded through a logical port of the OLT, the switching from the active OLT to the standby OLT cannot be implemented by searching for physical ports that are mutual backups, which makes a communication link unable to recover quickly.